Physician-authored summaries and commentary on the most important medical research, provided by the NEJM Group, a division of the Massachusetts Medical Society.
© Massachusetts Medical SocietyJuly 2022
To address the placebo effect of exercise, researchers compared structured exercise to presumably inert saline knee injections.
Proving that exercise programs improve symptoms of knee osteoarthritis (OA) is challenging; those interventions cannot be blinded in clinical trials, and substantial placebo effects are likely. In this novel randomised trial that involved 206 patients with symptomatic knee OA, researchers sought to isolate the placebo response.
Patients were randomised to an eight week exercise and education program (with 15 hours of contact with physical therapists) or to four intra-articular saline injections, spread over eight weeks; the latter intervention was considered to be inert placebo. The researchers noted that when saline has been used as a placebo control in randomised trials of injection therapies for knee OA, the magnitude of improvement with saline has been similar to that of exercise in other trials. Hence, the researchers assumed equipoise between the two interventions, and they openly disclosed this assumption with participants.
The primary outcome was change on a standardised 100 point OA pain scale. At nine weeks, mean improvement was 10 points with exercise/education and seven points with saline injections – a nonsignificant difference. No significant differences were noted for secondary outcomes that addressed physical function and quality of life.
Comment: This study suggests that a placebo effect explains much of the improvement that occurs with structured exercise programs for knee OA. That does not necessarily mean that we should totally abandon exercise interventions, for at least two reasons: first, average outcomes in clinical trials sometimes obscure benefits for individuals. Second, for some patients, exercise might confer general wellbeing that is not easily measured. Whether formal exercise programs are cost effective interventions for knee OA is another matter – a value judgement, beyond the scope of this study.
ALLAN S. BRETT, MD
Clinical Professor of Medicine, University of Colorado School of Medicine, Aurora, USA.
Bandak E, et al. Exercise and education versus saline injections for knee osteoarthritis: a randomised controlled equivalence trial. Ann Rheum Dis 2022; 81: 537-543.
This summary is taken from the following Journal Watch title: General Medicine.